A few tools that would assist you are SCUMM Revisited. This lets you look at a lot of the files. Perhaps more importantly for editing the game itself would be the "Resource File Creator and Dumper". This lets you extract an entire LAB archive from the game and then rebuild it, presumably after you edit one of the files. The difficulty is that the files are not really in a standard format, and perhaps altering them and rebuilding the .Lab files would break the way that data in them is accessed?

In summary, getting things out is okay, but the hard part would be putting them back into the game.